Pulmonary Embolism

• Pulmonary embolism (PE) refers to the obstruction of the pulmonary artery or one of its branches by a thrombus (or thrombi) that originates somewhere in the venous system or in the right side of the heart

Types • Most commonly, PE is due to a blood clot or thrombus. • However, there are other types of emboli: air, fat, amniotic fluid, and

septic (from bacterial invasion of the thrombus).

Risk Factors Venous Stasis (slowing of blood flow in veins) • Prolonged immobilization (especially postoperative) • Prolonged periods of sitting/traveling • Varicose veins • Spinal cord injury

Hypercoagulability (due to release of tissue thromboplastin after injury/surgery) • Injury • Tumor (pancreatic, GI, GU, breast, lung)• Increased platelet count (polycythemia, splenectomy)

Venous Endothelial Disease • Thrombophlebitis • Vascular disease • Foreign bodies (IV/central venous catheters)

Certain Disease States (combination of stasis, coagulation alterations, and venous injury) • Heart disease (especially heart failure) • Trauma (especially fracture of hip, pelvis, vertebra, lower extremities) • Postoperative state/postpartum period • Diabetes mellitus • Chronic obstructive pulmonary disease

Other Predisposing Conditions • Advanced age • Obesity • Pregnancy • Oral contraceptive use • History of previous thrombophlebitis, pulmonary embolism • Constrictive clothing

Pathophysiology

thrombus completely or partially obstructs a pulmonary artery

The area continue to be ventilated, but receives little or no blood flow.

gas exchange is impaired or absent in this area

the alveolar dead space is increased

V-Q mis match

various substances are released from the clot and surrounding area

causing regional blood vessels and bronchioles to constrict

increase in pulmonary vascular resistance.

Increases ventilation–perfusion imbalance.

• The hemodynamic consequences are increased pulmonary vascular resistance from the regional vasoconstriction and reduced size of the pulmonary vascular bed. • This results in an increase in pulmonary arterial pressure and, in turn,

an increase in right ventricular work to maintain pulmonary blood flow. • When the work requirements of the right ventricle exceed its

capacity, right ventricular failure occurs, leading to a decrease in cardiac output followed by a decrease in systemic blood pressure and the development of shock.

Clinical Manifestations • Tachypnea • Dyspnea • Anxiety • Chest pain • Hypoxemia may be present

depending on the size of embolism• Cough • Syncope (loss of consciousness)

• Hemoptysis • Crackles • Fever • edema • cyanosis

Diagnostic findings• Physical examination • Pulse oxymetry • ABG analysis • ECG• Lung perfusion scan • CT scan • Pulmonary angiography is the definitive means of diagnosis of PE

Medical Management• General measures to improve respiratory and vascular status • Anticoagulation therapy – heparin or warfarin, low mol.wt heparin• Thrombolytic therapy - streptokinase, alteplase, anistreplase,

reteplase• Surgical intervention

EMERGENCY MANAGEMENT• Nasal oxygen • Intravenous infusion lines • A perfusion scan, hemodynamic measurements, and arterial blood

gas determinations are performed. • Hypotension is treated by a slow infusion of dobutamine (Dobutrex)

(which has a dilating effect on the pulmonary vessels and bronchi) or dopamine (Intropin).

• The ECG is monitored continuously for dysrhythmias and right ventricular failure, which may occur suddenly. • If the patient has suffered massive embolism and is hypotensive, an

indwelling urinary catheter is inserted to monitor urinary output. • Small doses of intravenous morphine or sedatives are administered to

relieve the patient’s anxiety, to alleviate chest discomfort, to improve tolerance of the endotracheal tube, and to ease adaptation to the mechanical ventilator.

SURGICAL MANAGEMENT • Pulmonary embolectomy requires a thoracotomy with cardiopulmonary

bypass technique. • Transvenous catheter embolectomy is a technique in which a vacuum-

cupped catheter is introduced transvenously into the affected pulmonary artery. Suction is applied to the end of the embolus and the embolus is aspirated into the cup. The surgeon maintains suction to hold the embolus within the cup, and the entire catheter is withdrawn through the right side of the heart and out the femoral vein. • An inferior caval filter is usually inserted at the time of surgery to

protect against a recurrence.